The background description provided herein is for the purpose of generally presenting the context of the disclosure. Work of the presently named inventors, to the extent it is described in this background section, as well as aspects of the description that may not otherwise qualify as prior art at the time of filing, are neither expressly nor impliedly admitted as prior art against the present disclosure.
In many land-based oil and gas drilling operations, drilling rigs may be delivered to an oilfield drilling site by transporting various components of the drilling rig over roads, highways, and/or railroads. The various drilling rig components may be transported to a drilling site on one or more truck/trailer combinations, rail cars, or other modes of transportation, the number of which may depend on the size, weight, and complexity of the rig. Once at the drilling site, the drilling rig components may be assembled, and the drilling rig assembly may be raised to an operating position so as to perform drilling operations. After the completion of drilling operations, the drilling rig may be lowered, disassembled, loaded back onto truck/trailer combinations, rail cars, or other modes of transportation, and transported to a different oilfield drilling site for new drilling operations. Accordingly, the ease with which the various drilling rig components can be transported, assembled and disassembled, and raised and lowered can be a substantial factor in the drilling rig design, as well as the rig's overall operational capabilities and cost effectiveness.
Moreover, in particular parts of the world, access to cranes or other equipment for assembling and disassembling operations may be relatively limited and, in particular, the availability of large, high lifting cranes may be limited. Where a large drilling rig with a high floor height is desired to provide for deep drill depths and high drilling capacities, the absence of large crane availability may create difficulties or impasses in assembly and disassembly of drilling rigs.
In some applications, drilling operations at a given oilfield drilling site may involve drilling a plurality of relatively closely spaced wellbores, sometimes referred to as “pad” drilling. In pad drilling, the distance between adjacent wellbores may be as little as 20-30 feet or less in some applications. The plurality of wellbores are often arranged in a two-dimensional grid pattern, such that rows and columns of wellbores may be disposed along lines running substantially parallel to an x-axis and a y-axis, respectively. In such pad drilling applications, after drilling has been completed at one wellbore, the drilling rig may be moved to an adjacent wellbore. Often, after drilling operations have been completed at the pad site, the drilling rig may be relocated to a different drill site, which may also be a pad site.